JPH08296431A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PURPOSE: To restrain wastefuel energy consumption by controlling the generating voltage of an alternator in response to the detected operating condition of an engine by supplying electric power from the alternator to an electric-heating type catalyst. CONSTITUTION: Whether or not an ignition switch is turned on is judged, and when it is turned on, the detection values of an engine water temperature(TW) and an intake air temperature(TA) are read, and a TON, VEHC map determined in accordance with the TW, TA values is retrieved, and the energizing time of a heater resistance 24 and the supply voltage VEHC to an electric-heating type catalyst(EHC) are set for carrying out control. Then, it is discriminated whether or not an engine speed NE exceeds a prescribed speed NEK for judging perfect explosion, and when NE>=NEK, a changeover switch 23 is changed over to the side of a terminal 23c, and the output voltage of an alternator 21 is controlled so as to attain the previously set VEHC value for supplying electric power to the EHC. After the lapse of energizing time, the output voltage of the alternator 21 is reduced to the normal output voltage, and the changeover switch 23 is changed over to the side of the terminal 23b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying device for an internal combustion engine, and more particularly to a device having an electrically heated catalyst.

[0002]

2. Description of the Related Art A catalyst for purifying exhaust gas of an internal combustion engine needs time to be activated during cold start of the engine, and therefore it is electrically heated to accelerate its activation. Heated catalysts have been known for some time.

As an energization control method for the electrically heated catalyst, a desired energization time is set by setting an energization time according to the detected engine temperature and the like and supplying electric power from a battery for the set energization time. The one that can be obtained is conventionally known (Japanese Patent Laid-Open No. 4-27971).
No. 8).

[0004]

However, the above-mentioned conventional control method is a control in which only the energization time with the battery as the power source is used, and for example, when the engine (hot) is cold restarted as when the engine is hot restarted. When it is not necessary to supply a large amount of electric power, it is difficult to accurately control the energy supplied to the catalyst (integrated electric energy), and there is a tendency to consume more energy than necessary. Further, if the supplied energy is too large, the temperature of the catalyst excessively rises, and the durability of the catalyst deteriorates.

Further, since the battery is used as a power source,
Since it is necessary to supply a large current to the catalyst (heater), it is necessary to use peripheral circuit parts (switches and electric wires) with a large current rating, and there is room for improvement in this respect as well.

The present invention has been made in view of this point, and exhaust gas capable of accurately controlling the energy supplied to the electrically heated catalyst and reducing the supply current to reduce the cost of peripheral parts. An object is to provide a gas purification device.

[0007]

To achieve the above object, the present invention provides an alternator driven by an internal combustion engine to generate electric power, regulator means for controlling a generated voltage of the alternator, and an exhaust system of the engine. An electrically heated catalyst that is provided and that is electrically heated by the electric power generated by the alternator, an operating state detection unit that detects the operating state of the engine, and the electric heating according to the output of the operating state detection unit. An exhaust gas purifying apparatus for an internal combustion engine, comprising: a regulator control means for controlling a power generation voltage supplied to the electrocatalyst.

Further, it is preferable that the regulator control means further controls the time for supplying the generated voltage to the electrically heated catalyst in accordance with the detected engine operating condition.

Further, it is preferable that the operating state detecting means is at least one of a temperature of the engine, an intake air temperature and a temperature of an exhaust system of the engine.

[0010]

According to the exhaust gas purifying apparatus of the first aspect, electric power is supplied from the alternator to the electrically heated catalyst, and the power generation voltage of the alternator is controlled according to the detected engine operating state.

According to the exhaust gas purifying apparatus of the second aspect, the time for supplying electric power to the electrically heated catalyst is further controlled according to the engine operating condition.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an internal combustion engine and a control system therefor according to one embodiment of the present invention.
A throttle valve 3 is arranged in the middle of the intake pipe 2.
A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3 and outputs an electric signal according to the opening of the throttle valve 3 to supply it to the ECU 5.

The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). In addition to being electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 5, a valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5.

On the other hand, a pipe 7 is provided immediately downstream of the throttle valve 3.
The intake pipe absolute pressure (PBA) sensor 8 is provided via the, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 8 is supplied to the ECU 5. Further, an intake air temperature (TA) sensor 9 is attached downstream thereof,
EC is detected by detecting the intake air temperature TA and outputting the corresponding electric signal.
Supply to U5.

The engine water temperature (TW) sensor 10 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects the engine water temperature (cooling water temperature) TW, outputs a corresponding temperature signal and supplies it to the ECU 5.

An engine speed (NE) sensor 11 is provided around a cam shaft or crank shaft (not shown) of the engine 1.
A cylinder discrimination (CYL) sensor 12 is attached. The engine speed sensor 11 sends a TDC signal pulse at a crank angle position that is a predetermined crank angle before the top dead center (TDC) at the start of the intake stroke of each cylinder of the engine 1 (every 180 ° of crank angle in a 4-cylinder engine). The cylinder discrimination sensor 12 outputs a cylinder discrimination signal pulse at a predetermined crank angle position of a specific cylinder, and each of these signal pulses is supplied to the ECU 5.

In the exhaust pipe 13 of the engine 1, an electrically heated catalyst (hereinafter referred to as "EHC") 16, a start catalyst 17 and a three-way catalyst 18 are arranged in this order from the upstream side, and these catalysts are contained in the exhaust gas. Purify components such as HC, CO, and NOx. Here, the start catalyst 17 is a small catalyst provided mainly for purifying exhaust gas immediately after the engine is started.

A passage 14 for supplying secondary air is further connected to the exhaust pipe 13 upstream of the EHC 16, and an air pump 15 is provided in the middle of the passage 14.

The EHC 16 and the air pump 15 are ECUs.
5 and its operation is controlled by the ECU 5. Further, the three-way catalyst 18 is provided with a catalyst temperature sensor 19 that detects the temperature TCAT, and the detection signal is supplied to the ECU 5. Further, the alternator 21 driven by the engine 1 is connected to the ECU 5 via the regulator 22, and the generated voltage thereof is the ECU.
Controlled by 5.

The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, a central processing circuit (hereinafter referred to as a central processing unit). "CPU") 5b, storage means 5c for storing various calculation programs executed by the CPU 5b and calculation results, the fuel injection valve 6, the air pump 15, the EHC 16, the regulator 22.
It is composed of an output circuit 5d for outputting control signals such as.

The CPU 5b carries out a calculation process of the energization time TON of the EHC 16 and the supply voltage VEHC based on the above-mentioned various engine parameter signals, and outputs a control signal according to the calculation result.

FIG. 2 is a circuit diagram showing a connection state of the ECU 5, the alternator 21, the regulator 22, the heater resistance 24 of the EHC 16, the motor 27 of the air pump 15, and the battery 29. The EHC 16 of the present embodiment is designed to function as a heater by energizing the catalyst itself, and its resistance is represented as a heater resistance 24.

In the figure, the output side of the alternator 21 is connected to the terminal 23a of the changeover switch 23,
The terminal 23c of the changeover switch 23 is connected to one end of the heater resistor 24. The other end of the heater resistor 24 is grounded, and an EHC current sensor 25 for detecting the heater current IEHC is provided in the middle of the connecting line 31.

The terminal 23b of the changeover switch 23 is the positive electrode of the battery 29 and the terminal 26a of the on / off switch 26.
The terminal 26b is connected to one end of the motor 27. The other end of the motor 27 is grounded, and a pump current sensor 28 for detecting the pump current IAP is provided in the middle of the connecting line 33.

The negative electrode of the battery 29 is grounded,
The positive electrode is connected to the ECU 5.

The switches 23 and 26 are connected to the ECU 5 and can be switched by a control signal from the ECU 5. Normally, the switch 23 is in a state where the terminals 23a and 23b are connected as shown in FIG. 2, the switch 26 is in an off state, and switching control is performed as necessary immediately after the engine is started. Also, the connection lines 30, 32
Are connected to the EUC 5, and the ECU 5 detects the EHC voltage VEHC and the pump voltage VAP. Further, the current sensors 25 and 28 are also connected to the ECU 5, and their detection signals are supplied to the ECU 5. These current sensors 25 and 28 are provided to detect abnormalities such as disconnection.

FIG. 3 is a flow chart of a process for controlling power supply to the heater resistor 24.

In step S1, it is determined whether or not the precondition is satisfied (whether or not the ignition switch is turned on).
If it is not established, this process is immediately terminated. When the precondition is satisfied (when the ignition switch is turned on), the detected values of the engine water temperature TW and the intake air temperature TA are read (step S2). Next, the TON map and the VEHC map set according to the TW value and the TA value are searched, and the energization time (EHC on time) TON of the heater resistor 24 and the supply voltage VEHC to the EHC 16 are determined (step S3).

As shown in FIG. 4, the TON map is set so that the TON value tends to decrease as the intake air temperature TA increases and the engine water temperature TW increases. In addition, since the current is not supplied above the predetermined temperatures TAH and TWH,
TON is set to 0. The VEHC map is shown in FIG.
As shown in (a) and (b), the VEHC value tends to decrease as the intake air temperature TA increases and the engine water temperature TW increases. Therefore, EHC1
The power supplied to 6 is controlled as shown in FIG. The VEHC value is set to, for example, about 30V at the cold start. As a result, it is possible to reduce the supply current to about 1/2 as compared with the case where the power is supplied from the battery.

In the following step S4, the engine speed N
E is a predetermined rotation speed NEK for complete explosion determination (for example, 400 rp
m) or more, and if NE <NEK,
Immediately after finishing this processing, when NE ≧ NEK, the changeover switch 23 is switched to the terminal 23c side, and the alternator output voltage VALT is controlled so as to be the VEHC value determined in step S3, and the EHC 16 is supplied with electric power. Supply (step S5). And energizing time T
After the passage of ON, the alternator output voltage VALT is lowered to the normal output voltage VCHG (for example, 14.5V), and the changeover switch 23 is changed over to the terminal 23b side (step S6).

As described above, in this embodiment, not only the energization time of the EHC 16 but also the supply voltage can be changed according to the intake air temperature TA and the engine water temperature TW. Therefore, the energy (integrated electric energy) supplied to the EHC 16 can be changed. It is possible to control with high precision and suppress wasteful energy consumption. Also, E
The HC voltage VEHC is higher than the battery voltage, for example, 30
By setting the voltage to about V, the supply current can be reduced and the cost of peripheral components can be reduced. Further, by setting the output voltage of the alternator 21 to about 30V, the power generation efficiency of the alternator 21 can be improved.

The precondition in step S1 of FIG. 3 may be satisfied when the ignition switch is turned on and the engine water temperature TW and / or the catalyst temperature TCAT are below a predetermined temperature.

FIG. 6 is a timing chart of a control operation example in this embodiment. When the ignition switch is turned on at time t0 ((a) in the same figure), the ECU 5 sets the regulator control voltage VC for normal operation. Predetermined voltage VC1
To set the power generation mode 1 ((f) and (h) in the same figure).
When the starter is turned on at time t1 after the time TD (for example, the time required to turn the key (about 0.1 seconds)) has elapsed from time t0, the engine starts to rotate ((b) in the figure).
(C)), the alternator output voltage VALT increases to the battery charging voltage VCHG as the engine speed NE increases ((g) in the same figure).

When the engine speed NE reaches the complete explosion determination predetermined rotation speed NEK (time t2), the ECU 5 determines that the complete explosion has occurred ((c) and (d) in the same figure), and the switch 23 is set to the terminal 23b.
A switching control signal for switching from the side to the side 23c is output ((e) in the figure). At this time, considering the time required for switching the switch 23 (the time from the output of the control signal until the switching is actually completed, for example, about 0.25 seconds) ΔT, the regulator control is performed from time t2 to time t3 after ΔT. The voltage VC is set to the EHC control voltage VC2 such that the alternator output voltage VALT becomes the VEHC value determined in step S3 of FIG. 3, and the power generation mode 2 is entered ((f) and (h) in the figure). As a result, the alternator output voltage V
ALT increased to VEHC level (Fig. (G)), and EHC
The temperature of 16 starts rising ((i) in the same figure). here,
The EHC control voltage VC2 is feedback-controlled so that the detected supply voltage (voltage of the connecting line 30 in FIG. 2) matches the determined VEHC value.

Then, at time t4 after the time TON determined in step S3 of FIG. 3, the regulator control voltage VC is set to VC.
Return to HG value and return to power generation mode 1 ((f) in the figure)
(H)). As a result, the alternator output voltage VALT
Becomes the normal battery charging voltage VCHG ((g) in the same figure). The ECU 5 outputs a control signal for switching the switch 23 from the terminal 23c side to the side 23b at time t5 after the time ΔT has elapsed from time t4, and ends the control at the engine start ((e) in the figure).

In this embodiment, the air pump motor 27 is operated at the same timing as when the EHC 16 is turned on.

In the above-described embodiment, the voltage supplied to the EHC 16 and the energization time are both set according to the engine water temperature TW and the intake air temperature TA, but the energization time may be constant. Further, instead of either the engine water temperature TW or the intake air temperature TA, the catalyst temperature TCAT detected by the catalyst temperature sensor 19 is used to calculate the voltage VE.
CH and energization time TON may be set.
Alternatively, the voltage VEC may be changed in accordance with any one or two of the engine water temperature TW, the intake air temperature TA, and the catalyst temperature TCAT.
H and energization time TON may be set. Further, instead of the catalyst temperature TCAT, a parameter representing the temperature of the exhaust system such as the exhaust gas temperature may be used.

[0039]

As described in detail above, according to the present invention, electric power is supplied from the alternator to the electrically heated catalyst, and the generated voltage of the alternator is controlled according to the detected engine operating state. The energy (integrated electric energy) supplied to the catalyst can be accurately controlled, and wasteful energy consumption can be suppressed. Further, by setting the power generation voltage of the alternator higher than the battery voltage, it is possible to reduce the supply current to the electrically heated catalyst and reduce the cost of peripheral parts.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control system therefor according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a connection state of a heater resistance and the like of an electrically heated catalyst.

FIG. 3 is a flowchart of a process for controlling the voltage supplied to the electrically heated catalyst and the energization time.

FIG. 4 is a diagram showing a table used in the processing of FIG.

5 is a diagram showing a table and the like used in the processing of FIG.

FIG. 6 is a timing chart of a control operation example in the present embodiment.

[Explanation of symbols]

 1 Internal Combustion Engine 5 Electronic Control Unit 9 Intake Air Temperature Sensor 10 Engine Water Temperature Sensor 16 Electric Heating Catalyst 18 Three-Way Catalyst 21 Alternator 22 Regulator 23 Changeover Switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Teshirogi 1-4-1 Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Takuya Aoki 1-4-1 Wako-shi, Saitama Incorporated company Honda R & D Co., Ltd. (72) Inventor Hiroaki Kato 1-4-1 Chuo, Wako, Saitama Prefecture Incorporated Honda R & D Co., Ltd. (72) Inventor Taku Komatsuda 1-1-4 Wako-Chu, Saitama Incorporated Honda Technical Research Institute (72) Inventor Hideo Furumoto 1-4-1 Chuo, Wako, Saitama Incorporated Honda Technical Research Institute

Claims (3)

[Claims] 1. An alternator driven by an internal combustion engine to generate electric power, regulator means for controlling a generated voltage of the alternator, and an electric power generated by the alternator, which is provided in an exhaust system of the engine. An electrically heated catalyst to be heated, an operating state detecting means for detecting an operating state of the engine, and a regulator control means for controlling a power generation voltage supplied to the electrically heated catalyst according to an output of the operating state detecting means. An exhaust gas purifying apparatus for an internal combustion engine, comprising: 2. The internal combustion engine according to claim 1, wherein the regulator control means further controls a time for supplying the generated voltage to the electrically heated catalyst according to the detected engine operating state. Exhaust gas purification device. 3. The exhaust gas of an internal combustion engine according to claim 1, wherein the operating state detection means is at least one of a temperature of the engine, an intake air temperature, and a temperature of an exhaust system of the engine. Gas purification device.